XOG data rows from parent

What I have come up with so far is below but, "parentInstanceCode" is not recognised by XOG resulting in error "attribute "name" has a bad value: the value is not a member of the enumeration: ("instanceCode"/"objectCode")"

What should I be using in the below to bring back the records? For reference "bc" is the Master Object and "bc_approval" the subobject.